The discussion below is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.
The invention relates to a mooring assembly for a vessel, comprising a moonpool in said vessel having a casing, a turret positioned in said moonpool and mounted therein for a rotation around a turret rotation axis relative to said moonpool by means of an upper bearing assembly and a lower bearing assembly and mooring lines attached to a lower part of the turret, wherein the lower bearing assembly comprises a stiff inner bearing ring attached to said lower part of the turret, an outer bearing ring attached to the casing of the moonpool, a number of circumferentially spaced bearing blocks positioned between the inner and outer bearing rings for assuring a load transfer between the inner and outer bearing rings, and mounting means cooperating with said bearing blocks for maintaining a substantially fixed position of the bearing blocks relative to the outer bearing ring.
Apart from the mooring lines (which, for example, may comprise mooring chains) also risers (for example for oil or gas) may be attached to the lower part of the turret, as well as other equipment (for example drilling equipment). The turret allows the vessel to rotate (weathervane) in response to varying outer conditions (such as, for example, wind, waves and current) without disconnecting the mooring lines and risers. Generally the upper bearing (also sometimes referred to as main bearing) transmits most of the vertical forces (which in the major part are gravitational and acceleration forces due to the weight of the turret, mooring lines and risers). The lower bearing predominantly will be responsible for transmitting radial loads (which in the major part are mooring and riser loads) between the turret and the vessel.
The bearing blocks of the mooring assembly due to the provision of the mounting means substantially have a stationary position with respect to the outer bearing ring. In a state of the art mooring assembly the bearing blocks are housed or fixed in mountings attached to the outer bearing ring, in such a manner that the respective bearing forces between the inner bearing ring and outer bearing ring in majority are transmitted through these mountings. This, however, may lead to unfavorable conditions, among which stress concentrations at those locations in the outer bearing ring where these mountings are attached to the outer bearing ring.